Process and device for removing printer&#39;s ink from a fiber suspension

ABSTRACT

Method and apparatus for separating ink from pulped inked paper: a suspension of pulped paper and chemicals enters a cylindrical container tangentially near the container bottom and rotates around the interior of the container; the ink and chemicals form a foam that floats off the suspension of paper fibers; the suspension exits from the container tangentially near the container top; a funnel at the top of the container; a foam outlet near the axis of the container from the funnel; a vortex generator at the bottom of the container, which blows upwardly creating a vortex in the suspension; means disperse air in the suspension in the container inlet before the suspension enters the container through the container inlet; the dispersing means either comprises a rotor cooperating with a stator, or comprises deflector plates in the container inlet; air is supplied to the inlet at the dispersion means rotor or deflector plates; the deflector plates may be washed clean.

The invention relates to a process and to an apparatus for removingprinter's ink from a fiber suspension comprised of used paper whereinthe process comprises adding chemicals and air to the suspension andthen floating off a foam of the ink and chemical materials.

BACKGROUND OF THE INVENTION

Conventionally, de-inking of fiber suspensions of used paper isperformed in so-called flotation cells, in which air is suppliednaturally or is forced into the suspension in such a way that anintimate mixture of air and suspension occurs and dispersion of the airthrough the suspension results. The subsequent separation of air,together with the collectors and carriers, to which the printing inkparticles adhere, from the suspension occurs as a result of the buoyancyof the collectors and carriers which form a foam. The foam in which theprinting ink particles are carried floats and is then skimmed from theopen vessel off the surface of the suspension. The drawback of thisprocess is that under optimal conditions, the flotation cells canoperate only at material densities of about 1%. Higher materialdensities decrease the effectiveness of the process performed in thesecells. Furthermore, the power consumption of the conventional process isrelatively high.

SUMMARY OF THE INVENTION

The primary object of the invention is to provide a de-inking process ofhigh efficiency.

It is another object of the invention to be able to de-ink suspensionsof relatively higher densities.

It is yet another object of the invention to effectively and rapidlyseparate impurities from a fiber suspension of liquified paper.

This is accomplished according to the invention by flowing thesuspension through a rotation-symmetrical container in rotational motionand by the flotation foam being discharged from the container in thearea of the axis of rotation thereof.

Not only is the usual floating buoyancy of the foam of chemicals and inkused, but the radial pressure gradient and the effects of centrifugaland resisting forces, which are present in the whirling flow, are alsoused. This at the same time produces a low pressure gradient between theentrance and exit of the flotation vessel, which, in turn, has afavorable effect on power consumption.

The combined application of different fields of force, plus, possibly, aseparate, highly effective dispersion, allows the flotation process tobe performed with material densities of about 2%. Thus, fewer devicesare required for cleaning any specified quantity of material. Eitherplant space requirements may be reduced, or more fiber material can becleaned in a plant of the same size. As a further advantage, air can besupplied in a controlled manner. Moreover, the process is very simple.The process can also be carried out in a closed system. Thus, theenvironment would not be disturbed by odor or spray water.

A device for implementing the process according to the inventioncomprises a rotation symmetrical container preferably in the form of anupright cylinder, with an inlet relatively nearer to one end wall of thecylinder, an outlet for the cleaned fiber suspension relatively nearerto the other end wall, and a foam outlet in the area of the uppercylinder axis. In one embodiment of the invention, the inlet openstangentially into the cylinder.

Effective separation of the fibers from the dyestuffs is accomplished byarranging the outlet for deinked fiber suspension to extend laterallyfrom the upper area of the cylinder.

In a further development of the invention, the upper area of thecylinder is funnel-shaped and the foam outlet is arranged there. Thefunnel acts as a centering device for the foam and thereby increases theseparation effect.

In a further development, a propeller or rotor is placed in the lowerarea of the cylinder coaxially with the cylinder.

Formation of a vortex at the center of the cylinder is furtherintensified according to the invention by providing the lower end wallof the container, in the area of the cylinder axis, with an upwardlytapering cone. A liquid conduit opens into the interior of the cone.Liquid introduced into this area causes an upwardly directed rotaryflow. The liquid for this purpose may be either clear water or a part ofthe fiber suspension that must be cleaned. It is of advantage if an airconduit also opens into the interior.

Highly effective and intensive mixing of air and fiber suspension isaccomplished if dispersion means for effectively dispersing and mixingair throughout the suspension are arranged in the inlet line to thecylinder. This means includes an air feed line which delivers air to anarea of the inlet line in which the elements that cause the dispersionof air are arranged.

In one embodiment, the dispersion means may comprise a rotor, into whosearea the inlet lines for the suspension and for the air open, and astator designed as a filter, beyond which the outlet line for thesuspension mixed with air is located.

Preferably, the dispersion means is provided with an outlet forimpurities, which is arranged ahead or upstream of the filter. Thishelps eliminate disturbing impurities from the liquified suspensionprior to the flotation. Any light-weight impurities such as plasticmaterials passing through the filter can also be removed by therotational motion of the suspension in the container itself through thefoam outlet.

Static disperson elements without any moving parts comprise anotherembodiment of dispersion means. These comprise an arrangement ofdeflector plates and edges. Air that flows along with the suspensionover the plates and off their edges is broken up into fine bubbles andis intimately mixed with the fiber suspension. In a modified embodiment,the deflector elements are comprised of perforated plates. A furtherpossibility is to equip the deflector elements with a plurality ofdeflector plates which are arranged across the flow direction.

An arrangement of spray tubes for spraying water, or the like may bepositioned in the area of the deflector elements. The spray keeps thedeflector elements free from deposits.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and features of the invention are described below, withreference to the accompanying drawings, in which:

FIG. 1 is a longitudinal section through a device according to theinvention in which the process according to the invention is practiced;

FIG. 2 is a section through one dispersion means according to theinvention;

FIG. 3 is a section through another dispersion means according to theinvention;

FIG. 4 is a section through a third dispersion means according to theinvention; and

FIG. 5 is a longitudinal section through an alternate embodiment of adevice according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The device according to the invention comprises an upright cylinder 1. Asuspension comprised of liquified or pulped paper that has beenimprinted with ink and which liquified paper is combined with knownchemicals and carriers for floating ink out of the suspension, is mixedwith air and is then supplied laterally into the cylinder 1 via an inlet2, which is oriented to emit the mixed suspension and air into thecylinder in a generally tangential direction. The inlet 2 is above, butrelatively nearer to, the lower wall 6 of the cylinder. The suspensionof paper material, with the ink and the collectors therefor removed, isdischarged laterally at the upper area of cylinder 1 via an outlet 3.The outlet is also oriented to remove the material from the cylinder ina generally tangential direction. The outlet 3 is below, but relativelynearer to, the top section 5 of the cylinder 1. The relative verticalpositions of the inlet and the outlet might be reversed, but theillustrated arrangement is preferred.

Only the flotation foam carrying the removed ink is extracted centrallyupward through a foam outlet 4, which is located in the side wall offunnel-shaped top section 5 of the cylinder 1. The outlet 4 is alsooriented to withdrawn foam in a direction generally tangential to thefunnel. Because of this arrangement, no negative effects are produced bya breakout of the vortex core. At the same time, this arrangementenables the handling of large volumes of air at only low shearingforces. The end material outlet 3 is always free of air.

A core 7 projects upwardly from the lower end wall 6 of cylinder 1. Aliquid conduit 8 and an air conduit 9 both open into the interior ofcone 7. The liquid conduit 8 opens in a direction that is generallytangential to the cone 7 so that the vortex core is stabilized. Due tothe narrowing of the cone, the supplied liquid volume is greatlyaccelerated up to its exit from the cone and it enters the interior ofthe cylinder 1 at a high rotational velocity. This effect is intensifiedby the air flow via air conduit 9 which enters cone 7 at its centralaxis through lower end wall 6.

In a modification of this (FIG. 5), a propeller or rotor 26 is placedcoaxially in the container at the bottom thereof for generating theupward vortex. The cone 7, liquid conduit 8 and air conduit 9 could beeliminated.

In the first embodiment of FIG. 2, dispersion means 11 are arranged inthe inlet line 10 to cylinder 1. Means 11 are supplied with suspensionthrough line 12 and with air through line 13. The dispersion means 11comprises a motor-driven rotor 14 which is driven around a vertical axisin FIG. 2 by a motor (not shown) through a shaft 14a. A stator, designedas a filter 15 is positioned coaxially around the rotor 14. The fibermaterial to be mixed with air enters the dispersion means 11tangentially via inlet line 10 toward the cylinder 1. The coarse airbubbles mixed in the fiber material are broken up by the rotating rotor14 and the stator 15. Simultaneously, intimate blending and dispersionof air in the fiber suspension takes place.

The dispersion means also includes an outlet 16 upstream of the filterand having a blocking device 17 therein for periodic discharge ofimpurities retained by the filter 15.

Generally, the chemicals required for de-inking have been added alreadyto the suspension in a preceding pulper (not shown) upstream of thedispersion means. If they are required, still further chemicals can beadded directly into the dispersion means 11, the inlet line 10 or thecylinder 1 itself.

A second embodiment of dispersion means is shown in FIG. 3. It comprisesa central inlet tube 18 for delivering fiber material to the dispersionmeans. An air supply tube 19 supplying air from a source thereof (notshown) delivers air flow into the tube 18. The tube 19 delivers air tothe bottom of dispersion means 21. The means 21 is arranged in housing20, similarly to the dispersion means of FIG. 2. The dispersion means 4is a conically shaped, apertured, stationary filter that extends up thefull height of the housing 20 and narrows upwardly. A liquid spray tube22 communicating with a liquid supply (not shown) and with an outletinto the top of the filter 21 and aimed outwardly to spray the interiorof the filter 21 eliminates deposits on the dispersion means.

A third embodiment of dispersion means is shown in FIG. 4. It comprisesan installation of deflector plates 23 in a tube 24. Although a precisemeans for supporting the plates 23 stationary is not shown, theperipheral plates are carried on the interior of the tube and thecentral plates may be supported by wires (not shown) extending in fromthe periphery of the tube. The deflector plates are taperingly shaped ontheir inlet (left in FIG. 4) side to direct flow over and past theplates.

The suspension to be treated moves in the direction of the arrows. Airflows into air inlet 25, so that, as the air and suspension mixtureapproaches the plates, the air is divided into fine bubbles because ofthe pressure differences at the deflector plate edges.

In this embodiment, too, a cleaning device, spray nozzles 22, preventsclogging of the deflection plates.

Although the present invention has been described in connection withpreferred embodiments thereof, many variations and modifications willnow become apparent to those skilled in the art. It is preferred,therefore, that the present invention be limited not by the specificdisclosure herein, but only by the appended claims.

What is claimed is:
 1. A process for removing ink from a fibersuspension, which suspension was made from pulped inked paper, whereinthe suspension was made by the addition of chemicals to the pulped inkedpaper, comprising the steps of:introducing the suspension into acontainer relatively nearer to the bottom of the container; flowing thesuspension rotationally around the container, for causing the ink andchemicals to form a foam that separates from the suspension; removingthe suspension, from which the foam has separated, from the containerrelatively nearer to the top of the container; and discharging thefloating foam from the container in the vicinity of the axis of rotationof the suspension around the container and in the area of the axis ofthe container near the top of the container and above the removal of thesuspension.
 2. The process for removing ink from a fiber suspension ofclaim 1, wherein air is dispersed through the suspension prior to saidintroduction of the suspension into the container.
 3. The process forremoving ink from a fiber suspension of claim 1, further comprisingintroducing a liquid flow in a vortex starting at the bottom of thecontainer for generating a vortex of the suspension in the container. 4.The process for removing ink from a fiber suspension of claim 3, furthercomprising introducing an air flow into the container from the bottom ofthe container near the axis of the container.
 5. The process forremoving ink from a fiber suspension of claim 1, wherein the suspensionis introduced into the container along a direction that is tangential tothe container and the suspension is removed from the container alsoalong a direction that is tangential to the container.
 6. The processfor removing ink from a fiber suspension of claim 5, further comprisingintroducing a liquid flow in a vortex starting at the bottom of thecontainer for generating a vortex of the suspension in the container. 7.The process for removing ink from a fiber suspension of claim 5, furthercomprising introducing an air flow into the container from the bottom ofthe container near the axis of the container.
 8. Apparatus for removingink from a fiber suspension, which suspension was made from pulped inkedpaper, wherein the suspension was made by the addition of chemicals tothe pulped inked paper, comprising:an upright, substantially cylindricalcontainer having a bottom and a top; a suspension inlet for thesuspension and being located relatively nearer said bottom; a suspensionoutlet for the suspension and being located relatively nearer said topfor withdrawal of suspension from which the foam of chemicals and inkhas separated; a foam outlet nearer the top of said container than saidsuspension outlet and located in the area of the axis of said container;dispersion means in said suspension inlet and outside said container fordispersing air through the suspension passing through said suspensioninlet; said dispersion means comprises a rotor in said suspension inlet;one inlet line for suspension and a second inlet line for air and bothsaid inlet lines entering said suspension inlet inside said rotor; astator adjacent to said rotor; said stator being in the form of a filterand said filter being placed such that beyond said stator, thesuspension passes through said suspension inlet into said container; animpurities outlet from said suspension inlet between said rotor and saidstator filter.
 9. The apparatus for removing ink from a fiber suspensionof claim 8, wherein said container has a funnel-like section at the topthereof; said foam outlet being from said funnel-like section.
 10. Theapparatus for removing ink from a fiber suspension of either of claims8, or 9, wherein said suspension inlet enters said container laterally.11. The apparatus for removing ink from a fiber suspension of claim 10,wherein said suspension inlet enters said container in a direction whichdirects flow of suspension along a direction that is tangential to saidcontainer.
 12. The apparatus for removing ink from a fiber suspension ofclaim 10, wherein said suspension outlet leaves said containerlaterally.
 13. The apparatus for removing ink from a fiber suspension ofclaim 12, wherein said suspension outlet leaves said container in adirection which receives a flow of suspension that is flowing along adirection that is tangential to said container.
 14. The apparatus forremoving ink from a fiber suspension of claim 13, wherein saidsuspension inlet enters said container in a direction which directs flowof suspension along a direction that is tangential to said container.15. The apparatus for removing ink from a fiber suspension of either ofclaims 8 or 9, further comprising generating means near said containerbottom for generating an upward flow of suspension and for aiding increating a vortex in said container.
 16. The apparatus for removing inkfrom a filter suspension of claim 15, wherein said generating meanscomprises a rotor arranged coaxially to the axis of said cylinder. 17.The apparatus for removing ink from a fiber suspension of claim 15,wherein said generating means comprises an upwardly narrowingly taperingcone projecting up from said container bottom in the area of the axis ofsaid container; anda liquid supply conduit opening into said cone forgenerating an upward vortex in said cone and thereby for generating avortex in said container.
 18. The apparatus for removing ink from afiber suspension of claim 17, further comprising an air supply conduitopening into said cone.
 19. The apparatus for removing ink from a fibersuspension of claim 8, wherein said dispersion means comprises an airfeed line into said suspension inlet and comprises deflector elements insaid suspension inlet for deflecting flow of suspension mixed with airthereby to disperse air in the suspension.
 20. The apparatus forremoving ink from a fiber suspension of claim 19, wherein said deflectorelements are comprised of a perforated plate.
 21. The apparatus forremoving ink from a fiber suspension of claim 19, wherein said deflectorelements are comprised of a plurality of deflector plates supported andarranged across said suspension inlet in the flow direction ofsuspension through said suspension inlet.
 22. The apparatus for removingink from a fiber suspension of claim 20, further comprising spray tubemeans in said inlet for spraying said deflector elements.